Network systems exist in a number of different formats and protocols, and in a variety of different technology areas. Some of these network systems have built-in systems and methods for identifying failures within the network. Additionally, some network systems also attempt to re-route signals propagating through the network to avoid any revealed problems or failures.
One known network system, called Synchronous optical network (SONET), is a standard for optical telecommunications transport. The Exchange Carriers Standards Association for the American National Standards Institute defines one version of SONET protocol. The comprehensive SONET standard provides the transport infrastructure for worldwide telecommunications. SONET defines a technology for carrying many signals of different capacities through a synchronous, flexible, optical hierarchy. This is accomplished by means of a byte-interleaved multiplexing scheme. Byte-interleaving allows bytes from multiple different sources to be combined in a single system without losing track of each byte, and simplifies multiplexing because it offers a method by which each byte can be tracked.
SONET based systems can experience circuit failures from time-to-time. The term “circuit” as utilized herein shall mean a discernable path or route between a source node and a destination node. The circuit may or may not include intermediate nodes between the source node and the destination node. The circuit is disposed within a mesh topology as understood by one of ordinary skill in the art.
A common issue in current network schemes is the detection and correction of a failure along the path of an established circuit. If a failure occurs along the path, a network scheme must be able to identify or detect the failure condition and communicate the failure condition to the source of the circuit so that circuit protection/restoration action can quickly and efficiently be taken.
Other known network protocols include O Optical Network Protocols, and IP Network Protocols, which are understood by those of ordinary skill in the art.
One method for handling failures along a path of an established circuit is the use of a signaling protocol such as the label distribution protocol (LDP), or the Resource ReSerVation Protocol (RSVP). As utilized herein, the term label refers to a short, fixed length identifier used to determine the forwarding of a packet using an algorithm. The label is usually rewritten during forwarding. Label values are typically local to a single data link. A label switching device will usually replace the label in a packet with a different label prior to forwarding the packet to the next location. The label switching forwarding component uses a single forwarding algorithm in the form of forwarding tables based on label swapping to decide where to send the packets. The label distribution protocol is the standard by which label bindings distribute. The term label binding is an association between a label and a forwarding equivalence class (FEC), which can advertise to neighbors to establish a label switched path. The term forwarding equivalence class refers to a set of packets handled equivalently for the purposes of forwarding, and thus suitable for binding to a single label. Network layer routing protocols provide label switching routers with the mapping between FECs and a next forwarding address. The label binding information provides the label switching routers with the FECs and the labels. The two mappings combined provide the necessary information for forming the forwarding tables used by the label switching forwarding component.
If there is a failure along the path of an established circuit, the immediate node proximal to the failure must first successfully detect the failure. Once detection occurs, the node forwards an LDP message to the source of the circuit. In most instances, the mechanism by which the LDP message transports will require a period greater than 50 milliseconds. It is preferable in certain applications to receive notice of a failure and take action on that failure in a time less than 50 milliseconds from the initial failure.